A camera equipped with a zoom lens has so far been on the market. A zoom lens provides a change of a focal length (zooming) by moving a plurality of lens groups constituting an optical system to desired positions along the optical axis, and thereby, by changing their distances.
A method to move lens groups along the optical axis is divided roughly into two types. In one of them, a lens frame is engaged with a straight guide, and a cam cylinder or a helicoid is rotated to move the lens frame straight, and in the other of them, a shaft is arranged to be substantially in parallel with the optical axis to be a guide shaft, then, a frame that engages with the guide shaft is formed on the lens frame, and a motor and a lead screw are used to cause the lens frame directly to slide along the guide shaft for straight movement. As a driving source for moving these lens groups, a DC motor and a stepping motor are generally used.
On the other hand, there is known a so-called bending optical system whose optical axis is bent by a reflection surface arranged in the optical system. In a camera equipped with such an imaging optical system whose optical axis is bent, a lens barrel is not protruded from a front face of the camera in the course of photographing, and a form of the camera is not changed irrespectively of zooming operations, which is an advantageous point.
Even in the case of a camera employing this imaging optical system whose optical axis is bent, its outer shape is required to be small and thin, and an imaging optical system to be housed is required to have higher variable power. However, if the imaging optical system is made to have higher variable power, a tendency toward a greater total length of the optical system is unavoidable.
For the requirements mentioned above, there is a camera whose outer shape is made to be small to house an imaging optical system wherein plural reflection surfaces are arranged, and an optical axis is bent more than once so that the optical axis may not exist on the same plane (for example, see TOKUKAI No. 2004-193848).
A digital camera described in the aforesaid document provides a zoom lens with high variable power which can be housed in a camera with a small outer shape. However, when there is provided a digital camera in which an optical axis is bent more than once into optical axis segments and in which lens groups are arranged to be moved, in the case of zooming, along the respective optical axis segments not forming the same straight line, driving sources arranged for respective lens groups to move the lens groups increase cost and lens barrel size, which is a problem.